The present invention relates to an extruder and more particularly to a new and improved extruder screw.
In the manufacture of thermoplastic materials, the extruder receives the plastic material in its hopper and delivers such materials to a feed screw located in the extruder barrel wherein the extruder screw advances and then works the plastic materials to produce a homogeneous extrudate.
To enhance the plasticizing process of an extruder screw, various configurations of screws have been made wherein the flights which define the channel depth may be dual flighted to increase the working action or the pitch of the flights have been varied or a portion of the screw section has decreasing channel depth to increase working. All of these variations, however, do not enhance the processing of heat sensitive compounds.
The present invention is concerned with enhancing the processing of heat sensitive compounds because of the necessity to obtain a thorough homogeneous mix without overheating the mix. It is critical in the processing of these compounds to maintain good flow through the extruder or mixer while achieving a homogeneous mix at a lower final temperature. The quality of the end product was the important key and thus it was essential to process such plastic material without raising the melt temperature during the process which otherwise would destroy its optimal morphological structure. Such novel processing of heat sensitive compounds provides for a thorough homogeneous mixing with a complete heat transfer to the entire melt while maintaining a low processing temperature during the processing action as well as a final low temperature at the die end.